| 1. |
- Frydendal, Rasmus, et al.
(author)
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Benchmarking the Stability of Oxygen Evolution Reaction Catalysts: The Importance of Monitoring Mass Losses
- 2014
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In: ChemElectroChem. - : Wiley. - 2196-0216. ; 1:12, s. 2075-2081
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Journal article (peer-reviewed)abstract
- Because of the rising need for energy storage, potentially facilitatedby electrolyzers, improvements to the catalysis of theoxygen evolution reaction (OER) become increasingly relevant.Standardized protocols have been developed for determiningcritical figures of merit, such as the electrochemical surfacearea, mass activity and specific activity. Even so, when new andmore active catalysts are reported, the catalyst stability tendsto play a minor role. In this work, we monitor corrosion onRuO2 and MnOx by combining the electrochemical quartz crystalmicrobalance (EQCM) with inductively coupled plasma massspectrometry (ICP–MS). We show that a meaningful estimationof the stability cannot be achieved based on purely electrochemicaltests. On the catalysts tested, the anodic dissolutioncurrent was four orders of magnitude lower than the total current.We propose that even if long-term testing cannot be replaced,a useful evaluation of the stability can be achievedwith short-term tests by using EQCM or ICP–MS.
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| 2. |
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| 3. |
- Pedersen, Anders F., et al.
(author)
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Operando XAS Study of the Surface Oxidation State on a Monolayer IrOx, on RuOx and Ru Oxide Based Nanoparticles for Oxygen Evolution in Acidic Media
- 2018
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In: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 122:2, s. 878-887
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Journal article (peer-reviewed)abstract
- Herein we present surface sensitive operando XAS L-edge measurements on IrOx/RuO2 thin films as well as mass-selected RuOx and Ru nanoparticles. We observed shifts of the white line XAS peak toward higher energies with applied electrochemical potential. Apart from the case of the metallic Ru nanoparticles, the observed potential dependencies were purely core-level shifts caused by a change in oxidation state, which indicates no structural changes. These findings can be explained by different binding energies of oxygenated species on the surface of IrOx and RuOx. Simulated XAS spectra show that the average Ir oxidation state change is strongly affected by the coverage of atomic O. The observed shifts in oxidation state suggest that the surface has a high coverage of O at potentials just below the potential where oxygen evolution is exergonic in free energy. This observation is consistent with the notion that the metal-oxygen bond is stronger than ideal.
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| 4. |
- Siahrostami, Samira, 1982, et al.
(author)
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Enabling direct H2O2 production through rational electrocatalyst design
- 2013
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In: Nature Materials. - : Springer Science and Business Media LLC. - 1476-4660 .- 1476-1122. ; 12:12, s. 1137-1143
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Journal article (peer-reviewed)abstract
- Future generations require more efficient and localized processes for energy conversion and chemical synthesis. The continuous on-site production of hydrogen peroxide would provide an attractive alternative to the present state-of-the-art, which is based on the complex anthraquinone process. The electrochemical reduction of oxygen to hydrogen peroxide is a particularly promising means of achieving this aim. However, it would require active, selective and stable materials to catalyse the reaction. Although progress has been made in this respect, further improvements through the development of new electrocatalysts are needed. Using density functional theory calculations, we identify Pt-Hg as a promising candidate. Electrochemical measurements on Pt-Hg nanoparticles show more than an order of magnitude improvement in mass activity, that is, Ag-1 precious metal, for H2O2 production, over the best performing catalysts in the literature.
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| 5. |
- Stoerzinger, Kelsey A., et al.
(author)
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Orientation-Dependent Oxygen Evolution on RuO2 without Lattice Exchange
- 2017
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In: ACS Energy Letters. - : American Chemical Society (ACS). - 2380-8195. ; 2:4, s. 876-881
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Journal article (peer-reviewed)abstract
- RuO2 catalysts exhibit record activities toward the oxygen evolution reaction (OER), which is crucial to enable efficient and sustainable energy storage. Here we examine the RuO2 OER kinetics on rutile (110), (100), (101), and (111) orientations, finding (100) the most active. We assess the potential involvement of lattice oxygen in the OER mechanism with online electrochemical mass spectrometry, which showed no evidence of oxygen exchange on these oriented facets in acidic or basic electrolytes. Similar results were obtained for polyoriented RuO2 films and particles, in contrast to previous work, suggesting lattice oxygen is not exchanged in catalyzing OER on crystalline RuO2 surfaces. This hypothesis is supported by the correlation of activity with the number of active Ru-sites calculated by density functional theory, where more active facets bind oxygen more weakly. This new understanding of the active sites provides a design strategy to enhance the OER activity of RuO2 nanoparticles by facet engineering.
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